 \begin{tikzpicture}[
node distance = 2cm and 2cm,
     N/.style = {circle, draw, font=\Large, 
                 minimum size=1.1em},
       every edge/.style = {draw, -Stealth, semithick, shorten >=2pt},
every edge quotes/.style = {auto=right, inner sep=2pt}
]
% \node (m) at (0,0) {【例3.5】$\rm{L=\left\{a b^{n} c, b^{n} \mid n \geqslant 0\right\}, \Sigma=\{a, b, c\}}$}; 
\node (n) at (0,0){1.正规文法描述:};
\node (p) at ([xshift=6em,yshift=-2em]n.south){$\mathrm{G}(\mathrm{S}): \mathrm{S}\rightarrow \mathrm{aA}|\mathrm{bB}| \varepsilon, \mathrm{A} \rightarrow \mathrm{bA}|\mathrm{c}, \mathrm{B} \rightarrow \mathrm{bB}| \varepsilon$};
\node (v) at ([xshift=2em,yshift=-4em]n.south){2.正规式描述:$e =a b^{*} c \mid b^{*}$};
\node (x) at ([xshift=-1.5em,yshift=-2em]v.south){3.有限自动机描述:};
\node[N] (a) at ([xshift=7em,yshift=-1em]x.south)[label=left :{+ -}] {1};
\node[N] (b)[right of=a] {2};
\node[N] (c)[right of=b][label=right :{-}]{3};
\node[N] (d)[below of=b][label=right :{-}]{4};
\node (z) at ([xshift=-3em,yshift=0em]a.west){FA:};
\node(c1)[draw,rectangle callout,callout relative pointer={(1,1)},rounded corners,align=center] at ([xshift=-1em,yshift=-4em]z.west) {表示可接受\color{red}{空串}\color{black}{!}};
\draw [dashed,red]  ([xshift=1em,yshift=1em]a.south) arc[start angle=360,end angle=0,x radius=0.75,y radius=1];
\path
(a) edge [above] node {a} (b)
    edge [above] node {b} (d)
(b) edge [above] node {c} (c)
    edge [loop above] node {b} ()
(d) edge [loop above] node {b} ()
    ;
    \end{tikzpicture}